CA2049048A1 - Electro optical apparatus - Google Patents

Abstract

The invention is directed to an electro-optical rangefinding-type apparatus which uses electronic sensors to detect the position and orientation of the apparatus relative to a fixed point. Data from the sensors is relayed to a microprocessor which can calculate parameters such as range, horizontal distance and angle, vertical distance and angle, relative speed and magnetic bearing of a target objective, which are then displayed. A preferred embodiment of the invention is convertible between the functions of a stereoscopic binocular and a coincidence-type rangefinder and means are provided for converting the apparatus to and from the binocular and rangefinding modes.

Description

~O91/12491 2 3 ~ ~ 3 ~ 3 PCT/CA91/0003~

ELECTRO OPTICAL APPARAT~S
The present invention is directed to an electro-optical apparatus which may be used to measure the range, magnetic bearing or vertical distance between the apparatus and a single target objective, and which may also be used to measure range, vertical or horizontal distances: verti-cal or hori20ntal angles between two or more target objec-tives as viewe~ ~rom the perspective of the apparatus or ~he relative speed of a remote objective. The apparatus may also be used to measure the surface area or volume of a targe~ objective. In a preferred embodiment, the invention is also directed to a coincidence type optical rangefinder, and electro-optical means for conversion to or from a stereoscopic binocular.
Optical measuring devices, such as rangefinders, are known. Conventional rangefinders (e.g. of the type shown in Canadian patent nos. 456,703; 452,835; 580,335;
452,827: 460,869 and 478,857) feature a pair of windows through which light rays from an objective ente~ the range-finder. The light rays are reflected through a system of prisms or lenses so that duplicate images of the objective are realized in the observer's field of vision. The observer then causes the two images to be brought into coincidence by manipulating refracting means so as to cause refraction of the light comprising one of the images, thereby aligning it with the light comprising the other image and bringing the two images into coincidence. The refracting means are mechanically associated with a linear scale ~hich is calibrated such that the amount of displace-ment or rotation of the refracting means suf ficient tocause coincidence of the dual images is a function of the range of the objective, which can be read from the scale.
Conventional rangefinders have the disadvantage of limited mechanical and thermal stability and limited ranging accuracy. ~actors which influence this include the length of the base line between the windows through which light rays from an objective enter the rangefinder, the ~091/t2~91 PCT/CA91/nnO~
~ 2 -magnification of the image, the angular acuity of the human eye or photosensitive component used to align images into coincidence, the type of refracting element used and the precision o~ the associated mechanical linkage to the rang-ing scale. The accuracy of conventional optical range-finders also depends upon proper calibration between the scale and refracting element which may be upset by jarring of the instrument, or by changes in ambient temperature.
As a result o~ these sensitivities, convention~l optical range~inders must b~ frequently recalibrated to maintain aeeuracy.
R~nyefinders of the type shown in Canadian patents nos. 5~9,24~, ~56,703 and 452,835 are monocular ~evices, which generally are more difficult to use for an extended period of time than binocular devices. Stereo-scopic binocular optical rangefinders are known (e.g. Canadian patents nos. 889,411 and 931,345). However, such devices are not coincidence-type binocular optical rangefinders which provide coincident images to both eye-2~ pieces. Coincidence type optical rangefinders are general-ly considered to be more accurate and easier to use than stereoscopic optical rangefinders. However, conventional coincidence type optical rangefinders may not be converted for stereoscopic binocular viewing without significant light loss occurring at the beamsplitter.
Also, rangefinders illustrated by the prior art are only able to measure range. If other parameters or dimensions of an objective need to be measured, other means of doing so must be used.
The prior art discloses instruments which calcu-late parameters or data pertaining to an objective, and which display such data within the observer's field of vision. For example, U.S. patent 4,544,24~ discloses a system wherein information relevant to a remote instrument is displayed within the field of view of a microscope. The system disclosed by this patent requires a beam splitter to be placed between the microscope objective and the viewing ~'091/12~91 PCT/CA91/0~03 binoculars. Mirrors are used to reflect the digital dis-play from the remote instrument into the field of view of the viewing binoculars. This system therefore requires several separate pieces of equipment to work in tanàem and is not a single àevice which can calculate data.
U.S~ patent no~ 7~ teaches modifie~ bino-culars which serve as ~ com~ination optical/timing appara-tus, displaying digital in~ormation calculated by a chrono-meter within the observer's field of ~iew~
U~S~ patent no~ 4,429,g~0 teaches a Xeratometric device ~or attachment t~ a surgical microscope, for use in obser~ing and measuring the spherical surface of the cornea o~ the eye~
Each of the devices taught by the aforementioned U.S. patents show inventions where digital information is displayed within the field of view Ot an observer. How-ever, each of these devices has a narrow, specific applica-tion. None is a single instrument which permits the measurement or calculation of several parameters relating to dimensions or position of an objective, as selected by the operator of the device.
The present invention overcomes the disadvantages of the prior art by providing an electro-optical apparatus or instrument which can be used as a conventional monocular or binocular viewing instrument for measuring and calculat-ing a variety of parameters pertaining to one or more target objectives.
Such parameters may be selected from, but not limited to, the following: range, height, magnetic bear-ing, speed, surface area, geographic coordinates, or spatial distances between two points, (such as vertical or horizontal distances or angles between two or more remote points with vertical/horizontal separation as viewed through the eyepiece(s) of the instrument).
Conventional optical rangefinding systems employ mechanical means such as cams, levers and gears to transmit and translate the displacement of the refracting element to O91/1_~9~ PCT/CA91/nO0~
2 ~

useful information.
According ~o the present invention, such mechani-cal means are replaced to a great e~tent by electronic means. Parameters relatiny to the target objective are measure~ and calculated electronically by a microprocessor using inputtea data received from sensors. The number of mec~anical parts associated with the calculation and dis-play of in~ormation is reduce~, and the apparatus is more resistant to ~he e~f~cts of impact and fluctuations in ambi~nt t~mperature than are con~entional range~inders with t~e result that the frequetlcy with which the instrument n~ed~ to be recalibrated is greatly reduced.
Further, the utili2ation o~ a micropro_essor or microcontroller permits the user to test the device for minor error and recalibrate, if necessary~
In addition, the use of electronic sensors permits the calculated parameters to be displayed digitally if desired within the field of view of one of the eye-pieces, avoiding the need to read and interpret a linear type scale.
When using the invention, the observer selects the target objective, dual or split images of which appear in the fielQ of view of the instrument. The observer causes the dual ~or split) images to be brought into coincidence, by causing displacement of a refracting element, and selects a parameter relating to the target objective which is to be calculated, using a control panel mounted on the instrument~
The amount or degree of physical displacement of the refracting element which is necessary to maintain a single targ~t image within the observer's field of ~ision, is detected by an electronic sensor which tran~lates this information as directly as possible into an electrical signal which is relayed to a microprocessor, along with data from other electronic sensors which detect the hori-zontal and vertical displacement or orientation of the apparatus; and the azimuth orientation of the apparatus ~!0 91/12~91 rcT/c~9l/nno3~

2~9~
with respect to the natural magnetic lines of the earth.
The selected parameter is calculated by a microprocessor using electronic data received from the sensors. In one embodiment, the calculated parameter may be ~is~layecl wi~h-S in the observer's field of view by e.s. a ~ al displaysuperimposed through an eyepiece of the apparatus.
Prefera~ly, the invention takes the ~orm of bino-culars, which subject the observer to less eyestrain than a monocular device, and o~rs the additional advantage o~
bein~ easily portable. In ~he embo~iment o the invention which features .1ual eyepieces, means for adju~ting the distan~e between the eyepieces is preferably provi~ed, in order to allow for correct interpupillary alignment for a variety of users.
l~ In a preferred embodiment, the apparatus of the present invention may be quickly and easily convertecl to and from a binocular without overlapping or split coinci-dent imayes to a coincidence type optical rangefinder with coincident images for ranging target objectives.
In a further aspect, the invention is directed to means for converting a binocular to a coincidence type binocular optical rangefinder, thereby greatly enhancing the utility of the conventional binocular and the conven~
tional coincidence type optical rangefinder~ Such means may consist of a switchable beamsplitter which allows a binocular instrument having separated right and left hand optical paths of light between the entrance window(s) to the eyepieces, to be converted to a coincidence-type optical rangefinder where merging of the right and left 3~ optical paths occurs at the beamsplitter. This beamsplit-ter may be a partially reflective and partially transmis-sive type which is specially coated to àivide a beam oL
light into a pair of beams, or a dichroic type whicn is specially coated to àivide a beam of light into two distinctly different colour groups, or of the frustrated total reflection type.
Additionally, the invention is directed to a ~`091/12491 PCT/C~91/n(U)~-~, _ means of electronically sensin~ the displacemer.t o~ a refractive element(s). This refracting element~s) is employed to align the ima~es formed DV light entering the spaced entrance windows and thereby allows the determina-tion of taryet ranye. This refrai~tin~ element¦s) may betwo counteracting prism we~yes tPrmed a diasporam~ter, o~
ot11er means.
In one aspect, the invention provides an electro-optical rangefinder, comprising: (a) a housing having at l~ least one eyepiece therein; (b) two entrance windows within sai~ housing to receive Liyht b~ams radiated from an objec-tive; ~c) reflectiny meatls for directing sai~ Light beams to orm dual or split imayes of sai~ objective within the fielc of view of said eyepiece; ~à] coincidence sensor means, the adjustment of which causes said dual or split images to coincide within the field of view of said eye-piece; (e) a microprocessor which receives data in the form of an electrical signal from sai~ coincidence sensor from which the range of said objective is calculated.
A further aspect of the invention provides an electro-optical apparatus, comprising: (a) a casing having at least one eyepiece therein; (b) two entrance windows within saià casing to receive light beams radiated from an objective; (c) function/command selection means for said apparatus mounted on said casing; (d) reflecting means for directing said light beams to form dual or split ima~es of saià c~jective wit~in the field of view of said eyepiece;
(e) coinciaence sensor means, the adjustment of which causes said dual or split images to coincide within the field o~ view of said eyepiece; (f) vertical sensor means sensitive to the position an~l displacement of said appara-tus with respect to the gravitational lines of the earth;
(g) horizont~l sensor means sensitive to the hori~ontal pOsitiorl and displacement of said apparatus relative to 2 remote point; (h) _ompass sensor means; (i) a micro-processor which receives signals from said sensors and which calculates parameters relating to the position, ~Q91/12491 PCT/CA91/0003 ~ 7 ~ 2 0''1~ n,~
dimension and orientation of said objective, and (j) dis-play means for displaying said parameters to the operator of the instrument.
Another aspect of the invention provides an electro-optical apparatus, comprising: ~a~ a casing havina at least one eyepiece (b) a pair of spaced entrance windows at each end of said casing to receive light beams radiated from an objective; (c) reflecting means ~or directiny said lig~t beams to ~orm image~ of said objective witl-in said eyepiece, (~) sensor means which detect the relative position or orientation of said apparatus relative to said o~ective, (e) a microprocessor which receives input from said sensor means: (f) function selection means mounted on said casing, (g) display means for displaying parameters relating to the position, dimension or orienta-tion of said objective, as calculated by said micro-processor.
An additional aspect of the invention provides an electro-optical apparatus, comprising: (a) a casing having a pair of spaced entrance windows to receive light beams radiated from an objective: (b) a pair of eyepieces; (c) a beamsplitter for causing said light beams to be merged and then split into a pair of beams; (d) a first series of prisms or lenses which direct said light beams from said windows to said beamsplitter; (e) coincidence sensor means comprising: a refracting element coupled with electronic means for sensing the relative displacement of said refracting element; means for effecting displacement of said refracting element to cause refraction of one of said light beams wherein said refraction causes alignment of the dual or split images of said objective formed by said light beams into single coincident images; (f) sensor means selected from the group comprising: a horizontal sensor which senses the relative position or displacement of said apparatus with reference to a horizontal or azimuth plane;
a vertical sensor which senses the relative position or displacement of said apparatus with reference to the ~'091/1249l '~L~t~ PCT/CA91/0003 gravitational lines of the earth; an~ a compass sensor which electronically senses magnetic direction; (g) a second series of prisms or lenses which direct said bea~s from said beamsplitter to said eyepieces. (h) a micro-processor which receives input from said sensor means andsaid coincidence sensor means: ~i) function selection means mounted on said casing; (j~ display means for displayiny paramet~rs relating t~ the position, dimension or orienta-tion o~ sai~ objeetive, as calculated b~ said micro-proce~s~r.
In a further aspect, the invention provides anoptical system for causing two beams of electromagnetic radiation to be merged into a single beam and split into tw~ beams which are directed to means for sensing said radiation, cvmprising: a combination of prisms, each of which has a siàe face angled at 45, wherein said sicie faces are oriented substantially parallel to each other and are separated by a thin medium having a low index of refraction.
A further aspect of the invention provides a sensor comprising: a refracting element through which may be directed an incoming beam of electromagnetic radiation, wherein displacement of said refracting element causes refraction of said beam: electronic means coupled to said refracting element for electronically measuring the relative displacement of said refracting element and converting this information to an electrical signal which is transmitted to a m~croprocessor.
An adàitional aspect of the invention provides an electro-optical apparatus convertible between the functions of a binocular and a coincidence type optical rangefinder, comprising: (a) a casing having a pair of spaced entrance winàows to receive light beams radiated from an objective (b) a pair of eyepieces; (c) a beamsplitter comprising a pair of prisms each of which have at least one side face angled at 45 wherein said side faces are oriented substan-tially parallel to each other and are separated by a thin WO 91/12491 PCl`/CA91/()00~
2 ~
_ g _ medium of low refractive inde~; (d) means for causing the orientation of said prisms relative to each other to be convertible from a first pOsitiOIl wherein said prisms are separated by a thin layer of air sufficient to permit total internal reflection of said li~ht beams within said prisms and a second position wherein said prisms interface and t~e orientation of sai~ prisms relative to each other permits partial internal reflection of said li~ht beams wit~lin said prisms an~ partial transmission of said liyht bea~s across the in~erace of said prisms; (e) a first series of prism~
or lenses which direct saic light beams from ~ai~ windows to said beamspLitter; (f~ coincidence sensor medns compris-ing: a refracting element coupled with electronic me~ns or sensing the relative displacement of said refrac~in~
element; means for effectins displacement of said refract-ing element to cause refraction of one of said light beams wherein said refraction causes alignment of the dual images of said objective formed by said light beams into a coinci-dent beam; (g) sensor means selected from the group ~0 comprising: a horizontal sensor which senses the relative position or displacement of said apparatus with reference to a hori~ontal or azimuth plane; a vertical sensor which senses the relative position or displacement of said apparatus with reference to the gravitational lines of the ~5 earth, and a compass sensor which electronically senses magnetic direction; (h~ a secon~ series of prisms or lenses which direct said beams from said beamsl~litter to said eyepieces, (i) a microprocessor which receives input from said sensor means and said coincidence sensor means; (j) function selection means mounted on said casing; (k) display means for displaying parameters relating to the position, dimension or orientation of said objective, as calculated by said microprocessor.
A still further aspect of the invention provides an optical switchable beamsplitter which is convertible between an unswitched state and a switched state, compris-ing: a non-linear interface defined by a layer of liquid WO91/12~91 rCT/C,~91/000~

J~

crystal material sandwiche~ between the parallel faces of at least two beamsplitter components which are oriented such that, in said unswitched state, light beams incident upon said interface at anyles slightly greater than t~e critical angle of said interface will be totally internally reflected within said beamsplitter, and in said switched state, an electromagnetic field is applied across said interface causing light beams incident upon said interface to be 5plit into two polarization components, one of said polarization components being totally, or nearly totally r~fle~ted internally at said interface and the other of said polari~ation components being totally, or nearly totally, transmitted across said interface; and means for supplying AC or DC voltage across ~aid interface so that an electromagnetic field of sufficient intensity to cause uniform reorientation of the molecules of said liquid crystal material is applied to said interface in said swit-ched state.
An additional aspect of the invention provides an electro-optical apparatus convertible between the functions of a binocular and a coincidence type optical rangèfinder, comprising: ~a) a casing having a pair of spaced entrance windows to receive li~ht beams radiating from a target ob~ective; (b) at least one eyepiece; (c) an optical switchable beamsplitter which is convertible between an unswitched state and a switched state, comprising: a non-linear interface defined by 2 layer of liquid crystal material sandwicheà between the parallel faces of at least two beamsplitter components which are oriented such that, in said unswitc~ed state, light beams incident upon said interface at angles slightly greater than the critical angle of said interface will be totally internally reflec- -ted at said interface and in said switched state, an electromaynetic field is applied across said interface causing light beams inciden~ upon said interface to be split into two polarization components, one of said polari-zation components being totally, or nearly totally reflec-~091/12~91 ~CT/C~91/~003~
2 ~ 8 ted internally at said interface, and the other of saidpolarization components beiny totally, or nearly totally, transmitted across said interface, and means for supplying ~C or DC voltage across said interface so that an electro-magnetic field o sufficient intensity to cause uniformreorientation of the molecules of said liquid crystal material is applied to said interface in said switched state; (d) a first series o reflecting means or lenses which direct said light beams ~rom said windows to said switchable beamsplitter, (e~ coincidence sensor means comprising: a r~fractinc3 element coupled to eLectronie means for sensing the relative displacement of said re~rac-ting element, means for e~ectin~ dis~lacement of said re~racting element to cause refractioll of said Light beams which define dual images of said objective, wherein said refraction causes alignment of said dual images of said target objective resulting in a coincident image; (f) additional sensor means which may be selected from the group comprising: a horizontal sensor which senses the relative position or displacement of said apparatus with reference to a horizontal or a~imuth plane, a vertical sensor which senses the relative position or displacement of said apparatus with reference to the gravitational lines of the earth, a timing device or chronometer, and a compass sensor which electronically senses magnetic direction: (9) a second series of reflecting means, or lenses which direct said beams from said switchable beamsplitter to said eye-piece (h) a microprocessor or microcontroller which receives input from said coincidence sensor means and said additional sensor means, (j~ means for displaying para-meters relating to the position, dimension, orientation, or relative speed of s~id objective as calculated by said microprocessor or microcontroller, and (k) function selec-tion means.
These and other aspects of the invention will now be more particularly described with reference to the accompanying drawings, which illustrate preferred embodi-~O91/12~91 PCT/CA91/Onn3~
2 ~ 12 -ments of the invention.
Figure 1 shows a plan view of the interior of a preferred embodiment of the invention, with one of the eyepieces shown in exploded vie~i~
Figure lA is a plan view of the interior of another embodimènt of the invention~
Figure ~ shows a plan view of the embodiment of the invention whi~h is shown in Fi~ure lA.
Figur~ 3 is a schemati~ representation o~ a s~etion of the interface of a preferred form of switchable beamsplitt~r~
Fiyure 4 is an ilLustration of a preferred embodiment of switchable ~eamsplitter, according to the invention.
lS Figures 4A and 4B show an alternative embodiment of beamsplitter for use in one embodiment of the invention, namely a convertible binocular apparatus.
Figures 5 and 5A show a top perspective view of one embodiment of coincidence sensor.
Figure 5B shows a side view of one embodiment of coincidence sensor.
Figures 6, 7, 8A, 8B, 9A, 9B, lOA and lOB each illustrate representative applica~ions of embodiments of the invention, being depictions of representative target objectives as viewed by the observer through the eyepieces of the instrument.
The electro-optical apparatus 10 of the present invention consists of a casing 11 which has a pair of windows 1~, 13 for receiving light beams represented as 14, 15 from a target objective (not shown). The light beams 1~, 15 pass through objective lenses 1~, l7 and are reflec-ted by mirrors 1~, 19 at a 9u degree angle. Those skilled in the art will appreciate that the arrangements of lenses an~ prisms depicted in Figures 1 and lA are intended to illustrate representative pre~erred arrangement and that other equivalents are not excl~ded from the scope of this invention. For example, objective lenses 16, 17, could WO91/12491 PCT/CA91/0003~
- 13 - 2~ ~9 0 ~ ~
alternatively be a single lens or prism and/or a series of same and prisms 18', l9' could be used as an alternative to mirrors 18, l9~ If prisms are used as an alternative to mirrors, such prisms would preferably be pentaprisms which have the advantage of being able to continue to reflect light at an angle of 90 in the horizontal plane, e~en when having been subjected to slight jarring or displacemant.
Light beams l~, lS are directed to a beamsplitter 20~ ~eamsplitter 20 is capable of simultaneously merging incoming light beams l~, 15 and splitting the merged beam inta two beams 14', 15`, thereby providin~ the observer with dual images of the target objective.
Prism arrangements which are capable of merging incoming Light beams and split~ing the merged beam includ-ing the use of separate beam mixers and beam splitters, asknown to persons skilled in the art may be used as a beam-splitter and are within the scope of this invention.
The beamsplitter will preferably feature a low number of internal reflective surfaces thereby minimizing loss of light and promoting sharper resolution of the target objective. A conventional beamsplitter having an interface oriented to incident light at approximately 45 may be used. In this embodiment, the invention can func-tion either as an apparatus to calculate parameters relat-ing to a target objective or as conventional binoculars.However, if used as conventional binoculars, dual images of the target objective will appear in the eyepieces of the instrument, and these can be made to form a sinyle coinci-dent image by adjusting coincidence sensor 25, as more particularly discussed below.
In a preferred embodiment, the invention is convertible between the functions of a conventional bino-cular and an apparatus which is capable of measuring range and other spatial or geographic parameters or co-ordinates pertaining to a target objective.
A preferred means for achieving this result, (i.e. switching from a binocular instrument with separated ~'O91/~2491 PCT/C~91/0003~

right and left hand optical paths of light from entrance window to eyepiece, to a coincident type optical range-finder where mi~ing of the right an-l left hand optical paths of light occurs at the beamsplitter) uses a novel type of beamsplitter ("switchable ~eamsplitter") which constitutes another aspect of the invention.
Switchable beams~litters are illustrated in Fi~ures 1, 4, ~ ~nd ~3~ ~ne embodiment of switchable beamsplitter 7~a consists ~ two beamsplitting halves with reflecting surfaces which cau~es light entering the beam-spli~ter ~rom l~t and ri~ht hand entrance windows 1~, 13 to be ineid~nt UpOI~ an interface 31 consisting of a layer of liquid crystal material sandwiched between the beam-s~litting halves 32, 33. This interface 31 is composed Or materials and assembled with techniques utili~ed in the electro-optical and liquid crystal industries~
This type of switchable beamsplitter 20a uses the birefringement properties of liquid crystal materials, i.e.
the property of exhibiting a different index of refraction for each of two different plane polarizations of light. A
beam of light incident upon an optically non-linear surface such as a layer of liquid crystal material 2~ ir. contact with both halves 32, 33 of a beamsplitting prism will have two different critical angles which may be determined using Snell's Law, the refractive index of the prism material, and the two refractive indices of the liquid crystal material. The interface 31 of the beamsplitter 20a and the liquid crystal may be so designed that when an apparatus equipped with a beamsplitter of the type described is to be used for stereo binocular viewing ("unswitched mode"), the layer of liquid crystal material 24 at the interface 31 between the beamsplitter halves 32, 33 is not in the presence of an electromagne-ic field sufficient of inten-sity to cause reorientation of the liquid crystal mole-cules. Light which is incident upon the interface 31 ofthe beamsplitter 20a from either side at slightly greater than the critical angle, is totally internally reflected, ~'091/12491 PCT/C~91/000~

- 15 - ~ 8 and there is no mi~ing across the beamsplitter interface of the right and left hand optical paths of light from the entrance windows or the eyepieces.
~en the apparatus is placed in the '`swi~che~
mode", i.e. when binocular coincidence type range~inding is desired, the layer of liqui~l crystal material 2i is subjec-ted to an electromagnetic field of sufficient intensity to cause reorientation of the liquid crystal molecule~, such reori~ntation causing light whic~ is incident upon the int~r~aca 31 cf the beamsplitter halves 32, 33 and liqui~
crystal material 24 at slightly greater than the critical angle, to be divided into first and second polarized compo-nents, one polarized component being internally reflected while the other polarized component is transmitte~ across the interface and into the beamsplitter half to become collinear with the reflected polarized component from light incident upon the interface and originating from the opposite entrance window of the apparatus.
This is schematically illustrated in Figure 3, where the solid lines represent beams of light which are reflected at the beamsplitter interface, while the dotted lines represent beams of light which are transmitted across the beamsplitter interface~ Therefore, in the unswitched mode as described, beams of light 'a' and 'd' incident upon the beamsplitter interface 31 of the beamsplitter halves and the liquid crystal material, are totally internally reflected. In the switched mode as described, beams of light 'a` and `d' incident upon the beamsplitter interface 31 are divided into polarization components, respectively 'b` and 'f' and 'e` and 'c'. The `b` and 'c' polarization components are internally reflected, while the 'e' an~ 'f' components are transmitted across the liquid crystal material ~ to become collinear respectively witn reflected components 'b' and 'c'. Thus, collinear components 'b' and 'e' and collinear components 'f' and 'c' consist of light beams which originate from both entrance windows of the apparatu~ lO. Where this type of switchable beams?litter WO91/12491 PCT/CA91/0003~
S~

is employed as a component of the convertible binocular/coincidence type optical rangefinder, separate images are formed in each eyepiece when the apparatus is in the unswitched mode, and dual or split images are formed to allow coincidence type optical rangefinding in one or both eyepieces when the apparatus is in tha switched mode, allowing the user to a~just thes~ images into coincidence.
This type of beamsplitter is well suitea to tha ~unctional requirements o~ a convertibl~
binocular/c~incidence type optical rat~ye~inder of the present invention as it allows the apparatus to be used as a binocular without significant transmission or reflection light loss at the beamsplitter, and then as a coincidence type binocular optical rangefinder with coincident images l~ provided to both eyepieces. These coincident images may be of the overlapping type where two complete images are brought into coincidence by superimposing one image upon the other, or of the split-image type where a single image is divided vertically, horizontally, or otherwise and is brought into coincidence by alignment of the image parts.
In one possible embodiment of this type of beam-splitter, the halves 32, 33 may be of dense flint glass, such as SF-lO, with a refractive index of approximately 1.728. A first coating 8 of a thin transparent electrode coating of about 3QO angstroms thickness is applied to the face of each beamsplitter half which meet to form the interface of the two beamsplitter halves. Indium tin oxide (ITO) is commonly used as an electrode coating although other coatings may also be used. This coating is necessary to impose an electromagnetic field upon the liquid crystal material at the beamsplitter interface sufficient in inten-sity to cause uniform reorientation of the liquid crystal molecules and thus effect splitting of light incident upon the interface into first and second polarized components.
A surface alignment layer 9 is deposited as a second coating on top of the transparent electrode coating and serves to uniformly align the liquid crystal material '0 91/12491 rcl~/c,~

-- 17 -- ~ A
at the interface. This surface alignment layer is commonly a spin coated polymer that is unidirectionally rubbed along the desired plane of the liquid crystal material. Other means of alignment of the liquid crystal material 2~ may be used, e~g, the oblique deposition of a thin film (approxi-mately 100 angstroms) of silicon monoxide.
The beamsplitter hal~es 3~, 33 are then assembled with a thin layer of liquid crystal 2~ of about 1~ microns sandwiche~ between the beamsplitter halves 32, 33. This interface 31 may be then seale~ from dust and atmosphere u~ing Teflon* yasXet material, or other means. The liquid ~rystal material 2~ used in this model is known by names such as ZLI-392~* and is availabla though BD~ in Canada or E.~ hemicals in the ~.S. ~LI-392~ has an No of about 1.52 and an Ne of about 1.72. This combination will provide total internal reflection, in the unswitched mode, of light incident upon the beamsplitter interface 31 of greater than about 1.1 radians and provide nearly total transmission of one polarization component in the switched mode for a wide range of angles of incidence at the inter-face from about 1.1 radians to about 1.4 radians. Various combinations of refractive indices of the glass which makes up the beamsplitter halves 32, 33 and of the liquid crystal material 24 may be used depending on the desired results.
~5 To provide total internal reflection in the unswitched mode for the lowest angles of incidence upon the interface, and nearly fifty percent reflection of a first polarization component and nearly fifty percent transmission of a second polarization component, in the switched mode for the largest range of angles of light incident upon the inter-face, it is necessary to selec~ liquid crystal material with a large delta N, and with its Ne nearly equivalent to the refractive index of the beamsplitter glass, and a No as low as possible so as to permit total internal reflection at the lowest possible angles of incidence upon the beamsplitter interface. Other means for reducing the acceptable angles of incidence at the interface (such as a *Trade-Mark ~'091/12491 PCT/CA91/0003 L~

Brewster angle polarizer), or other means may also be used.
The apparatus would also use AC voltage supplied to the two electro~e coatings layered on the beamsplitter halves, of about 15 volts rms at aroun~ l ~Hz. DC voltage may also be utilized, however a longer life for the liquid crystal material may be obtaine~ by the use of A~ voltage.
An alternative, but less preferred form o~
switchable beamsplitter 20b consists o~ an arrangement of l~ prisms fe~turing sides angled at 45 oriented substantially parallel to each other. The prisms comprising this type o~
alternative switchable beamsplitter 20b are convertible between a ~irst unswitched mode where an apparatus equipped with such a beamsplitter may be used as a binocular and a lS second switched mode where the apparatus can be used as a rangefinder. In the unswitched mode the prisms (as shown in Figure 4A) are separated by a thin medium 36a having a low index of refraction such as air, sufficient to permit total internal reflection of the incoming light beams 14, 15 within both prisms, and disallowing mixing of light ~eams within the prisms~ When beamsplitter 20b is in this first position, no mixing of the incoming light beams 14, 15 will occur at the interface 3~, and the images appearing in either eyepiece will be a single image of the target objective.
When switchable beamsplitter 20b is in the switched mode, the prisms comprising beamsplitter are in very close proximity to each other (as shown by Figure 4B) and are separated by a thin medium of low refractive index 36a which allows partial transmission of light beams 14, 15 across interface 36 and partial internal reflection within the prisms, known in the ar' as "frustrated total reflec-tion"~ ~eams 14, l~ are accordingly merged and split.
This permits images from both light beams 14, 15 to be viewed in either eyepiece of the apparatus. When the dual images are brought into coincidence, calculation of para-meters relating to the target objective may be effected, as ~'O 91/t2491 PCT/CA91/~003' 19- 2~
will be more particularly described below.
~ risms comprising beamsplitter 20b can be orien-ted relative to each other and moved to and ~rom switche~
and unswitched modes shown in Figur~s 4A and 4B by mechani-caL gearing (not illustrated) or other means whi~h allowsone or both of the prisms to be slightly moved rel~tive to the position of the other.
once beams 14' and 15` exit the bea~splitter, they are refl~ted through a series of mirrors, prisms and/or lenses shown by 21a, ~lb, 21c, 21d an~ 2~a, ~2b, 22c and 2~d in Figure 1 w~lich depicts ~ rcpresentative or pref~rred arrangement. In Figure 1, the depicted arranye-ment inclu~es mirrors 21a, 22a while in Figure lA prisms 21b and 22b include pentaprisms. Erecting lens 42, 42a may be used to invert the image into an upright image. Many variations or combinations of prisms or lenses could be employed to transmit beams 14 and 15 from the beamsplitter to eyepieces 23a, 23b, as will be understood by those persons skilled in the art.
Beams 14' and 15` will be perceived by an obser-ver through eyepieces 23a, 23b as dual or split images of the target objective. The dual or split images are brought into coincidence by the observer through adjustment of coincidence sensor 25.
- 25 Coincidence sensor 25 comprises refracting element(s) such as 26a, 26b or 26c, coupled with electronic position sensor 30 which senses the position or relative displacement of the refracting element(s). When the refracting element(s) is displaced, it causes refraction of light beam 14, which has emanated from the target objec-tive. Coincidence sensor 25 serves as a means for aligning dual or split images of the target objective in coinci-dence, as observed through the eyepieces 23a, 23b of the apparatus by translating the relative physical displacement of the refracting element into an electrical signal, and relaying this signal to a microprocessor 27 for processing.
In one embodiment of coincidence sensor 25, two WO91~12~91 2 ~iJ~ PCT/CA91/000 low power wedge type prisms 26a, 26b serve as refra~ting element and are aligned parallel with respect to each other and are capable of rotating counter-directionally as shown in Figure l. Refl-actiny elements 26a, 2~b are placed in front of one of tlle primary objective lenses such that light will enter refracting elements ~a and ~b be~ore entèring lens l6~ ~
An alternatlve ~orm of coincidence sensor 25 as ~own in Figures 5, 5A and 5B, may use a flat refractive glass plat~ ~e having paraLlel sides as the refracting el~ment. other means for effecting re~raction of light beams are known ~y tho~e skilled in the art ~ay also be used as refracting element and are within the scope of this invention~
Refracting element ~such as 26a, 26b, or 26c) is coupled to electronic position sensor 30, which is a posi-tion verification device which can measure or indicate rotary or linear motion, and may be an analog component such as a variable resistor or variable capacitance compo-nent such as a potentiometer or variable capacitor or a digital component such as a digital optical encoder or combination thereof. Analog siynals will be converted to digital signals before processing by the microprocessor.
Displacement of refracting element(s) (such as 26a, 26b or 26c) is effected by the observer using mechanical adjust-ment means 29. Incoming beam l~ is refracted to align with incoming beam l5 such that the dual images of the target objective form coincident images as observed through the eyepiece ~3a, 23b of the apparatus. When the refracting element~s) is displaced, the light beam 14 is refracted, the extent of such refraction being proportional to the ~egree of rotation or relative displacement of the refract-ing element, as shown by the dotted outline of refracting element 26c in Figurè lA, and by Figures 5 and 5A.
The amount of displacement of the refracting element(s) is inversely proportional to the remoteness of the target objective whose image is formed by light beams.
When the dual images of the target objective, as seen WO91/12~91 PCTJCA91/nO03 - 21 ~ J~
through the eyepieces of the apparatus, are brought into coincidence, the amount of displacement to wllich refracting element(s) has been subjected is measured by sensor 30 which converts this data into an electrical signal which is relaye~ to microprocessor 27 by lead 28.
In a preferred embodiment of the invention, improved focusing means are provided tv aid the user in aligniny dual imayes of the objective into coincidence.
The sp~ctrum of tl~e light beams entering the beamsplitter are divided at the intar~a~e of the beamsplitter 20, 20a or 2~b, to form two distinctly ~i~ferent color images at the eyepiece to assist the user~ in precisely aligning the images into coinciuence. This is achieved by coating one or both faces of the interfacing beamsplitter components with a dic21roic coatiny 3~ This coating is designed in such a way that at select angles of incidence, light trans-mitted through the dichroic coating 3 will be a distinctly different color from liyht wllich is reflected from the dichroic coating 3. In the case of the optical switchable beamsplitter, this coating may be applied before or after the application of the transparent electrode coatings 8, 9 to one or both faces of the interfacing beamsplitter compo-nents 32, 33. With the dichroic coating 3 in place, when the optical switchable beamsplitter 20a is in the unswitch-ed mode, light transmitted through the dichroic coating 3will be totally reflected at the interface 31 and will form su~stantially naturally colored images.
When the optical switchable beamsplitter 20a is in the switched mo~e for rangefinding, one polarization component will be divided into two distinctly different color groups, transmittiny one color group (e and f in Figure 3) across the interf~ce 31 of the two beamsplitter components 32, 33 and reflecting a second color group (b and c in Figure 3) at the interface of the two beamsplitter components.
Effectively, this division of a portion of the naturally reflected light into two distinctly different ~`091/12491 rCT/CA91/0003 ~ 22 - `
color groups will assist the user in precisely aligning dual images into a single coincident imaye for the purpose of ranging a taryet. When the dual images are out of coincidence, the images will each lac~ a portion of the full natural spectrum of light reflected by the target, and will therefore appear to be dif~erently colored~ If the ~ual imayes are not precisely in coincidence, different colored frinyes will appear on the periphery o~ the images.
When the dual images are aligned in perfect coincidence, the sin~le target image ~ormed will contain nearly the full spectrum o~ light re~lected by the target itself and will therefore appear naturally colored.
If the device according to the present invention is intended for use in calculating dimensions or para~eters l~ in addition to range, the device may be equipped with one or more additional sensors 39, 40, ~l and/or a timing device or chronometer 55.
Horizontal sensor 39 electronically senses the angular displacement of the instrument on a horizontal or azimuth plane with reference to a fixed point, e.g. a ground reference, magnetic pole, or astronomical reference point, while the apparatus is held or fixed, e.g. mounted on a tripod~ Displacement of the instrument as measured by the horizontal sensor 39 is translated to an electronic signal which is relayed to microprocessor 27.
The apparatus may also be equipped with a compass sensor 41, which may be a type of horizontal sensor. A
compass sensor consists of an electronic magnetic direction finding component, one type of which is referred to as a Flux Gate Sensor, and sold by KVH Industries of Rhode Islar.d, U~S~A.
Equipped with such a compass sensor 4l, the apparatus can also be used to calculate the maynetic bear-ing of the target objective~
Vertical sensor 40 is a vertical displacement sensor which electronically senses the angular displacement of the instrument on a vertical plane with reference to the WO91/12491 PCTtCA91/0003~
- 23 - ` `2~ n~8 natural yravitational lines of the earth. Vertical sensor 40 can take numerous forms. Vertical sensor 40 could be an electrolytic level sensor such as those manufactured and sold by The Fredericks Company of Pennsylvannia, U.S.A.
An apparatus ~eaturing a horizontal sensor 39 and vertical sensor 40 can be used to calculate height, as well as horizontal or vertical distances or angles between two remote points~
Tha number and type of dimensions or parameters which can be calculated by the apparatus will depend upon the number and type o~ sensors with which it is equipped.
Se~aral different combinations or permutations of sensors are there~ore poscible and accordingly a number of diffe-rent instruments having varying capabilities can be lS constructed and all are within the scope of this inven-tion.
The ~ollowing Table shows several different combinations of features with which the invention can be equipped and the corresponding parameters of the target objective which can be determined by an apparatus so equip-ped.
Apparatus Parameters of E~uipped with: Target Objective 1 - Coincidence sensor Range 2 - Coincidence sensor and horizontal Range; distance sensor and/or angle bet-ween two points in a horizontal plane 30 3 - Coincidence sensor and compass Range; distance sensor and,/or angle between two points in a horizontal plane: magnetic bearing 4 - Coincidence sensor and vertical Range: distance sensor and/or angle between two points in a vertical plane WO91/12491 ~ PCT/CA91/0003 5 - Coincidence sensor and vertical Range; distance sensor and horizontal sensor and/or angle bet-ween two points in a vertical and/or horizontal plane;
surface area 6 - Coincidence sensor and vertical Range; distance sensor and compass sensor and~or angle bet-ween two points in a horizontal and/or vertical plan~; magnetic bearing; surface area 7 - C~inci~ence sensor and hori~ontal Range: distance sensor and chronometer and/or angle bet-ween two points in a horizontal plane; speed (in horizontal plane) 8 - Coincidence sensor and compass Range; distance sensor and chronometer and/or angle bet-ween two points in a horizontal plane, magnetic bearing; speed tin a horizontal ~ plane) 9 - Coincidence sensor and vertical Range; distance sensor and horizontal sensor and and/or angle chronometer and/or angle between two points in a horizontal and/or vertical plane; speed (in a horizontal and/or vertical plane) l0 - Coincidence sensor and vertical Range; distance sensor and compass sensor and and/or angle chronometer between two points in a horizontal and/or vertical plane; surface area; speed (in a horizontal and/or vertical plane) Once beams 14', 15' exit from the beamsplitter these are reflected to the eyepieces 23a, 23b, where the images may be viewed by the observer. Information from the W09l~l2~9l PCT~CA91/0003~
- 25 - 2~
sensor(s) and chronometer (where present) are fed to micro-processor 27 which uses such information to enable it to calculate dimensions or parameters of the target objective, such as range, height, magnetic bearing or relative speed, as selected by the operator. Data from microprocessor 27 may be relayed to digital display 43 which ma~ be a clear LCD display placed within an image plane so that the para-meter as calculated by microprocessor 27 is di~played with-in the observer's fiel~ of view. If memory storage capa-1~ ~ity additional to that of the microprocessor is desired,the apparatus may optionally contain a memory storage module.
The invention further provides means for improv-ing ranging accuracy by increasing the magnification of one or both images appearing at the eyepieces, and/or placing photosensitive components such as a CCD (charge coupled device) or photodetector arrays in the image plane of one or both paths of light before or after the beamsplitter so that following initial resolution of coincident images with the aid of the human eye, greater resolution of the coinci-dent images may be achieved with the aid of the photosensi-tive component.
3 = ranging error A = angular acuity of human eye or photosensitive component D = distance to target M = imaye magnification B = baseline between instrument light entrance windows ~ D = + AD2 _ _ _ _ _ MB
Although other passive rangefinder devices uti-lize CCD's or photosensitive devices there exists some confusion in situations where there is difficulty in isolating a desired target image for ranging, especially where more than one object is within the field of view.

W091/12491 PCT/CA91/0n03 ~ 26 -The present invention serves to alleviate these difficul-ties by employing the human eye and brain to initially select the desired target image, by adjusting separate images into coincidence and thereby limiting the selection of contrast produciny images to a much narrower range of ~istances, allowing greater selectability of data available from the photosensitive components~ This seleetion o~ data will take place within the microprocessor or microcontrol~
lar.
Although the scope of the invention also includes a monocular device of the same basic construction, the preferreu embodiment of tlle invention features dual eye-pieces, sinee binocular viewing produces less eye strain than monocular viewing. ~lost binoculars or field glasses are àesigned such that there is a hinge which joins each of the two telescopes which form the binocular. This hinge allows the distance between the eyepieces to be adjusted to accommodate the interpupillary distance of various users.
Because it is convenient to embody this invention in a single housing, other means of adjusting correct inter-pupillary alignment must be provided. One means for accomplishing this entails one eyepiece beiny moved laterally with respect to the other. In doing so however, it becomes necessary to maintain a constant length of the light path to the eyepiece which is moved to prevent image defocusing. One way to achieve this entails moving eye-piece 23b and eyepiece mirror 22a to increase or decrease the distance between the eyepieces while moving erecting prism 42a a distance equal to half the movement of eyepiece 23b and eyepiece mirror 22a as shown in dotted outline in ~`igure l. This will ensure that the length of the optical path remains constant.
Xepresentative fielas of view of the apparatus as shown by eyepieces 23a, 23b is depicted in Figures 6, 7, ~A, 8B, 9A, 9B, l0A and lOB. In Figure 6 the apparatus is functioning as a conventional binocular. ln Figures 7, 8A, 8B, 9A, 9B, l0A and l0B, the apparatus is functioning as a ~'O91/12491 PCT/CA91/0003~
- 27 - 2~-~9~
measurement device and observer sees the target objective, together with data àisplayed digitally~
When operating the apparatus subject of the present example of the invention when ranging, or usinc3 the apparatus to measure other parameters the observer looks through the eyepieces, sees dual or split images of the target objective, an~ brings these into coincidence ~y manipulating coincidence sensor 25.
Figure 8A illustrat~s what the observer sees wh~r~ the target o~jective is the sailboat. The dual imag~s of the sailboat have ~een brought into coincidence, but dual images of the background lighthouse remain. I~ it is desired to ranye the lighthouse, the dual images are brought into coincidence, w1~ich means that there are dual lS images of the sailboat in tha foreground, as s11own by Figure 8B. In each case, the calculated parameters are displayeà.
The observer then selects the function or para-meter which is desired to be calculated by means of making appropriate selections or entries on control pads or swit-ches on instrument panel 53. Instrument panel 53 includes a button or pad enabling the operator to select a desired parameter to be calculated (SELECT switch 45), a button or pad enabling the operator to select whether reading of the selected parameter are to be calculated in metric or Enylish system or other systems of measurement (METRIC~ENGLISH switch 46), a button or pad which when pushed, causes data ~rom the sensors to be entered/relayed to microprocessor (ENTER switc`n 47); and a button or pad which fixes the digital display of parameters, to enable t~e data to be recorded if desired ~FREEZE/UNFREEZE switch 48), and an onjoff switch 49, and a calibration switch.
T~e functions or parameters selected by the observer are calculated by microprocessor 27 using data received from sensors 25, 39, 4~, 41 and chronometer 55.
The parameters calculated by microprocessor 27 are then relayed to digital display 43 and the information appears WO9l/1249l PCT/CA91/0003' ~`? ~ ~ ;i3~

in the observer's field of view within eyepiece 23.
Optionally, the invention may also include an exterior digital display panel 52 upon which the information m~y ~lso be displayed.
In order to ensure that the optical systems o~
the instrument have uniform properties of expansion an~
contraction when subjected to differ~nces in temperature, and to increase sl~ock absorbance and resistance of the instrument to temperature fluctuations, thereby r~ducing the need f~r frequent recalibr~tion of the instrument, prism~ an~ ~amsplitter 20 ~ay be secured to a mounting plat~ 50 wllich is secured to housing 11.
~ nlike in~rared or laser rangefinders, the device of the present invention does not require a large power source, but can be powered by means of power pack 51 which can be batteries.
Optionally, the invention can be mounted on a tripod (not shown) by means of tripod mount secured to the housing of the instrument.
Examples of possible applications of possible embodiments of tlle instrument subject of this invention are illustrated by means of the following examples:
Example 1 -In one embodiment of the invention when the on/off switch of the instrument is in the "off" position, no digital display will appear in the eyepieces and the apparatus can be used as conventional binoculars, as shown by Figure ~, which shows an airplane as the target objec-tive~
Example 2 - RANGE, HEIGHT, AND MAGNETI~ BEARING FUNCTION
Alternatively, the instrumer.t can also be used as a binocular coincidence type optical rangefinder, when the instrument is turned on and the coincidence sensor used to bring dual or split images of the target objective into coincidence.
In pushing the SELECT switch, the operator can select one or more functions wllich will calculate various ~'O91/t2491 PCT/CA91/0003~
2 ~

parameters. Figure 7 shows a bir~ as the target objec-tive.
In this example, when the instrument is turne~
on, the first function selectea will display the symbols for range, height, and magnetic bearing~
To reaà a sinyle object, such as the bird in this example, tlle operator adjusts the coinci~ence sensor until a single, coincident clear imaye appears, then rea~s the calculate~ data ~ro~ the eyapiece display:
5 m -range of bird ~rom operator 83.~ m -height o~ bird above operator's eyes.
156 -magnetic bearing If àesired the reaàings can be held within the eyepiece display and to ào so the operator pushes the FREEZ~jUNFREEZE switch~ The readings may then be recorded if desire~.
The operator may then push the SELECT switch to choose another function.
Exam~le 3 - VERTICAL OUTPOI~TS FUNCTION
This function relates points with vertical separation and may be used to determine vertical distance and angle between points. The function may be used when the apparatus is hand held or mounted on a tripod.
To select this function, the operator pushes the SELECT switch, and reads the symbols. To read the vertical distance of the pinnacle of the temple shown in r`igures 9A
and 9B above its base, in this example the operator sights the base, aàjusts the coincidence sensor and pushes the ENTER switch. He then sights the top of the pinnacle, and resets the coincidence sensor.
The readings are àisplayed within the eyepice:
3l.4 m -vertical distance between ba~e and pin-nacle.
63.72 -vertical angle between base and pinnacle.
35 317 -magnetic bearing.
These readings can be held within the field of display by pushing the FREEZE/UNFREEZE switch. The read-WO 91/~2491 PCI/CA91/()O03:`
r~
~ 30 --ings may then be recorded if uesired.
Either push ENTER switch, may be pushed to re-start this function, or the SELECT switch for a different function.
Example 3 - HORIZONTAL OUTPOINTS F~NCTION
This function may be used to determine horizontal plane relations between two points. This is a handheld or trip~d mount function of the apparatus which relates points with both vertical and horizontal separation. This func-tion may be used to datermine vertical distance and anglebetween points, and horizontal or slant distance and angle between points.
To select this function, the operator will push the SELECT switch, and read the symbols for horizontal outpoints. To read the vertical and horizontal relations between the base of the right buttress, to the top of the arch of the temple shown in Figures lOA and lOB, in this example, the operator sights the base of the buttress, adjusts the coincidence sensor and pushes the ENTER switch.
The top of the arch is then sighted and the coincidence sensor is again adjusted.
The readings are displayed within the eyepiece display:
27.3 m -vertical distance between base and arch.
51.64 -vertical angle between base and arch.
29.4 m -slant distance between base and arch.
16.84 -horizontal angle between base and arch.
These readings can be held within the eyepiece display by pushing the FREEZE/UNFREEZE switch. The read-ings may then be recorded if desired.
Either the ENTER switch may be pushed to restartthis function, or the SELECT switch to choose a different function.
The precedins examples illustrates a sample of the many number of routines which may be created to measure one or more parameters, by using data gathered by sensors or combinations of sensors which are capable of sensing W091/12491 PCT/CA91/0003' - 31 ~
range, vertical displacement, horizontal displacement, compass bearing, or time, and are not to be read as limit-ing the scope of the invention.

Claims (39)

CLAIMS:

1. An electro-optical rangefinder, comprising:
(a) a housing having at least one eyepiece therein;
(b) two entrance windows within said housing to receive light beams radiated from an objective;
(c) reflecting means for directing said light beams to form images of said objective within the field of view of said eyepiece;
(d) coincidence sensor means, the adjustment of which causes said dual or split images to coincide within the field of view of said eyepiece;
(e) a microprocessor which receives data in the form of an electrical signal from said coincidence sensor from which the range of said objective is calculated.

2. An electro-optical apparatus, comprising:
(a) a casing having at least one eyepiece;
(b) a pair of spaced entrance windows at each end of said casing to receive light beams radiated from an objec-tive;
(c) reflecting means for directing said light beams to form images of said objective within said eyepiece;
(d) sensor means which detect the relative position and orientation of said apparatus relative to said objec-tive;
(e) a microprocessor which receives input from said sensor means;
(f) function selection means mounted on said casing;
(g) display means for displaying parameters relating to the position, dimension and orientation of said objec-tive, as calculated by said microprocessor.

3. An apparatus as claimed in claim 2 wherein said sensor means is a coincidence sensor comprising a refrac-ting element coupled with electronic means for sensing the relative displacement of said refracting element; means for effecting displacement of said refracting element to cause refraction of one of said light beams wherein said refrac-tion causes alignment of the dual or split images of said objective formed by said light beams into coincident images; wherein the relative displacement of said refrac-ting element as measured by said electronic means is trans-mitted by an electrical signal to said microprocessor.

4. An apparatus according to claim 3 which additionally comprises a horizontal displacement sensor sensitive to the horizontal position and displacement of said apparatus relative to a remote point.

5. An apparatus according to claim 3 which additionally comprises a vertical displacement sensor sensitive to the vertical position and displacement of said apparatus relative to a remote point.

6. An apparatus according to claim 3 or 5 which additionally comprises a compass sensor.

7. An apparatus according to claim 3 which addition-ally comprises a horizontal displacement sensor sensitive to the horizontal position and displacement of said appara-tus relative to a remote point and a vertical displacement sensor sensitive to the vertical position and displacement of said apparatus relative to a remote point.

8. An electro-optical apparatus, comprising:
(a) a casing having at least one eyepiece therein;
(b) two entrance windows within said casing to receive light beans radiated from an objective;
(c) function/command selection means for said appara-tus mounted on said casing;
(d) reflecting means for directing said light beams to form dual or split images of said objective within the field of view of said eyepiece;

(e) coincidence sensor means, the adjustment of which causes said dual or split images to coincide within the field of view of said eyepiece;
(f) vertical sensor means sensitive to the position and displacement of said apparatus with respect to the gravitational lines of the earth;
(g) horizontal sensor means sensitive to the horizon-tal position and displacement of said apparatus relative to a remote point;
(h) compass sensor means;
(i) a microprocessor which receives signals from said sensors and which calculated parameters relating to the position, dimension and orientation of said objective; and (j) means for displaying said parameters to the operator of the instrument.

9. An apparatus according to claim 4, 6, 7 or 8, which additionally comprises a chronometer.

10. An electro-optical apparatus, comprising:
(a) a casing having a pair of spaced entrance windows to receive light beams radiated from an objective;
(b) a pair of eyepieces;
(c) a beamsplitter for causing said light beams to be merged and then split into a pair of beams;
(d) a first series of prisms or lenses which direct said light beams from said windows to said beamsplitter;
(e) coincidence sensor means comprising: a refrac-ting element coupled with electronic means for sensing the relative displacement of said refracting element; means for effecting displacement of said refracting element to cause refraction of one or said light beams wherein said refrac-tion causes alignment of the dual or split images of said objective formed by said light beams into single coincident images;
(f) sensor means selected from the group comprising:
a horizontal sensor which senses the relative position or displacement of said apparatus with reference to a horizon-tal or azimuth plane; a vertical sensor which senses the relative position or displacement of said apparatus with reference to the gravitational lines of the earth; and a compass sensor which electronically senses magnetic direc-tion;
(g) a second series of prisms or lenses which direct said beams from said beamsplitter to said eyepieces:
(h) a microprocessor which receives input from said sensor means and said coincidence sensor means;
(i) function selection means mounted on said casing;
(j) display means for displaying parameters relating to the position, dimension or orientation of said objec-tive, as calculated by said microprocessor.

11. An electro-optical apparatus convertible between the functions of a binocular and a coincidence type optical rangefinder, comprising:
(a) a casing having a pair of spaced entrance windows to receive light beams radiated from an objective;
(b) a pair of eyepieces;
(c) a beamsplitter comprising a pair of prisms each of which have at least one side face angled at 45° wherein said side faces are oriented substantially parallel to each other and are separated by a thin medium of low refractive index;
(d) means for causing the orientation of said prisms relative to each other to be convertible from a first posi-tion wherein said prisms are separated by a thin layer of air sufficient to permit total internal reflection of said light beams within said prisms and a second position where-in said prisms interface and the orientation of said prisms relative to each other permits partial internal reflection of said light beams within said prisms and partial trans-mission of said light beams across the interface of said prisms;
(e) a first series of prisms or lenses which direct said light beams from said windows to said beamsplitter;
(f) coincidence sensor means comprising: a refracting element coupled with electronic means for sensing the relative displacement of said refracting element; means for effecting displacement of said refracting element to cause refraction of one of said light beams wherein said refrac-tion causes alignment of the dual images of said objective formed by said light beams into a coincident beam;
(g) sensor means selected from the group comprising:
a horizontal sensor which senses the relative position or displacement of said apparatus with reference to a horizon-tal or azimuth plane; a vertical sensor which senses the relative position or displacement of said apparatus with reference to the gravitational lines of the earth; and a compass sensor which electronically senses magnetic direc-tion;
(h) a second series of prisms or lenses which direct said beams from said beamsplitter to said eyepieces;
(i) a microprocessor which receives input from said sensor means and said coincidence sensor means;
(j) function selection means mounted on said casing;
(k) display means for displaying parameters relating to the position, dimension or orientation of said objec-tive, as calculated by said microprocessor.

12. An apparatus as claimed in claim 10 wherein said mixer splitter prism means consists of a combination of two prisms wherein each of said prisms has one side angled at 45° and such prisms interface with each other along said 45° angle sides, separated by a medium having a low index of refraction.

13. An apparatus as claimed in claim 3, 10 or 11 wherein said refracting element is a refractive plate.

14. An apparatus as claimed in claim 3 wherein said WO 91/12491 PCT/CA9l/00035 means for electronically determining the relative displace-ment of said refracting element is an analog or digital electronic position sensor or combination thereof.

15. An apparatus as claimed in claim 10 or 11 wherein said electronic means for sensing the relative displacement of said refracting element is an analog or digital electro-nic position sensor or combination thereof.

16. An apparatus as claimed in claim 10 or 11 wherein said first or second series of prisms includes a penta-prism.

17. An apparatus as claimed in claim 10 or 11 wherein said parameters are selected from the group consisting of range; height; vertical plane and angle relations between two points; horizontal plane and angle relations between two points; surface area; geographic coordinates and magne-tic bearing.

18. An apparatus as claimed in claim 3, 4, 5, 6, 7, 8 or 9 wherein said means for displaying said parameters comprises a digital display which displays said parameters within at least one of said eyepieces.

19. An apparatus as claimed in claim 10 or 11 wherein said display means comprises a digital display which dis-plays said parameters within at least one of said eye-pieces.

20. An apparatus as claimed in claim 18 which comprises an additional digital display for displaying said parameters wherein said additional digital display is mounted on said casing.

21. An apparatus as claimed in claim 19 which comprises an additional digital display for displaying said WO 91/12491 PCT/CA9l/00035 parameters wherein said additional digital display is mounted on said casing.

22. An apparatus as claimed in claim 1, 2, 3, 4, S, 7, 8, 10, 11, 12 or 14 wherein said apparatus is mounted on a tripod.

23. An apparatus as claimed in claim 1, 2, 3, 4, 5, 7, 8, 10, 11, 12 or 14 wherein said apparatus is powered by batteries, or a rechargeable power supply.

24. An optical system for causing two beams of electromagnetic radiation to be merged into a single beam and split into two beams which are directed to means for sensing said radiation, comprising: a combination of prisms, each of which has a side face angled at 45°, where-in said side faces are oriented substantially parallel to each other and are separated by a thin medium having a low index of refraction.

25. A sensor comprising:
a refracting element through which may be directed an incoming beam of electromagnetic radiation, wherein displacement of said refracting element causes refraction of said beam; electronic means coupled to said refracting element for electronically measuring the relative displace-ment of said refracting element and converting this information to an electrical signal which is transmitted to a microprocessor.

26. An electro-optical coincidence type rangefinder, comprising:
(a) a casing having a pair of spaced entrance windows to receive light beams radiating from a target objective, (b) at least one eyepiece;
(c) beamsplitter means for causing said light beams to merge;

WO 91/12491 PCT/CA9l/00035 (d) a first series of reflecting means or lenses which direct said light beams from said windows to said beamsplitter means;
(e) coincidence sensor means comprising: a refrac-ting element coupled to electronic means for sensing the relative displacement of said refracting element; means for effecting displacement of said refracting element to cause refraction of said light beams wherein said refraction causes coincident alignment of dual images of target objec-tive formed by said light beams;
(f) additional sensor means which may be selected from the group comprising: a horizontal sensor which senses the relative position or displacement of said apparatus with reference to a horizontal or azimuth plane;
a vertical sensor which senses the relative position or displacement of said apparatus with reference to the gravitational lines of the earth, and a timing device or chronometer; and a compass sensor which electronically senses magnetic direction;
(g) a second series of reflecting means or lenses which direct said beams from said beamsplitter to said eyepiece;
(h) a microprocessor or microcontroller which receives input from said sensor means and said coincidence sensor means;
(i) control panel means; and (j) display means for displaying parameters relating to the position, dimension, orientation, or relative speed of said objective calculated by said microprocessor or microcontroller;

27. An optical switchable beamsplitter which is convertible between an unswitched state and a switched state, comprising:
a non-linear interface defined by a layer of liquid crystal material sandwiched between the parallel faces of at least two beamsplitter components which are oriented WO 91/12491 PCT/CA9l/00035 such that, in said unswitched state, light beams incident upon said interface at angles slightly greater than the critical angle of said interface will be totally internally reflected within said beamsplitter, and in said switched state, an electromagnetic field is applied across said interface causing light beams incident upon said interface to be split into two polarization components, one of said polarization components being totally, or nearly totally reflected internally at said interface and the other of said polarization components being totally, or nearly totally, transmitted across said interface; and means for supplying AC or AC voltage across said interface so that an electromagnetic field of sufficient intensity to cause uniform reorientation of the molecules of said liquid crystal material is applied to said inter-face in said switched state.

28. A beamsplitter as claimed in claim 27 wherein said parallel faces are each coated with a thin transparent conductive film and said parallel faces are additionally coated with a thin surface alignment layer to cause uniform alignment of said liquid crystal material in the unswitched state.

29. A beamsplitter as claimed in claim 28 wherein said electrically conductive film is indium tin oxide.

30. A beamsplitter as claimed in claim 28 or 29 wherein said surface alignment layer is a film of silicon monoxide.

31. A beamsplitter as claimed in claim 28, 29 or 30 wherein said surface alignment layer is a spin coated polymer.

32. A beamsplitter as claimed in claim 27, 28, 29, 30 or 31 wherein said beamsplitter additionally comprises internal reflecting means which cause light beams entering said beamsplitter to be reflected by 180 degrees so that light beams exiting said beamsplitter are substantially parallel with light beams entering said beamsplitter.

33. A beamsplitter as claimed in claim 27, 28, 29, 30, 31 or 32 wherein each of said components has a first reflecting face orientated such that light beams entering said beamsplitter will be reflected to be incident upon said interface at an angle slightly greater than the critical angle of said interface in said unswitched state;
and a second reflecting face orientated to said first reflecting face at substantially 90 degrees.

34. A beamsplitter as claimed in claim 27, 28, 29, 30, 31, 32 or 33 wherein one or both of said parallel faces are coated with a thin dichroic film so that in said un-switched state, light beams reflected at said interface will form substantially natural colored images, and in said switched state, one polarization component will be divided into two different color groups, one of said color groups being transmitted across said interface, and the other of said color groups being reflected at said interface.

35. An electro-optical apparatus convertible between the functions of a binocular and a coincidence type optical rangefinder, comprising:
(a) a casing having a pair of spaced entrance windows to receive light beams radiating from a target objective;
(b) at least one eyepiece;
(c) an optical switchable beamsplitter which is convertible between an unswitched state and a switched state, comprising: a non-linear interface defined by a layer of liquid crystal material sandwiched between the parallel faces of at least two beamsplitter components which are oriented such that, in said unswitched state, light beams incident upon said interface at angles slightly greater than the critical angle of said interface will be totally internally reflected at said interface and in said switched state, an electromagnetic field is applied across said interface causing light beams incident upon said interface to be split into two polarization components, one of said polarization components being totally, or nearly totally reflected internally at said interface and the other of said polarization components being totally, or nearly totally, transmitted across said interface; and means for supplying AC or DC voltage across said interface so that an electromagnetic field of sufficient intensity to cause uniform reorientation of the molecules of said Liquid crystal material is applied to said inter-face in said switched state;
(d) a first series of reflecting means or lenses which direct said light beams from said windows to said switchable beamsplitter;
(e) coincidence sensor means comprising: a refrac-ting element coupled to electronic means for sensing the relative displacement of said refracting element; means for effecting displacement of said refracting element to cause refraction of said light beams which define dual images of said objective, wherein said refraction causes alignment of said dual images of said target objective resulting in a coincident image;
(f) additional sensor means which may be selected from the group comprising: a horizontal sensor which senses the relative position or displacement of said apparatus with reference to a horizontal or azimuth plane, a vertical sensor which senses the relative position or displacement of said apparatus with reference to the gravitational lines of the earth, a timing device or chronometer and a compass sensor which electronically senses magnetic direction;
(g) a second series of reflecting means, or lenses which direct said beams from said switchable beamsplitter to said eyepiece;
(h) a microprocessor or microcontroller which receives input from said coincidence sensor means and said additional sensor means;
(j) means for displaying parameters relating to the position, dimension, orientation, or relative speed of said objective as calculated by said microprocessor or micro-controller; and (k) function selection means.

36. An apparatus as claimed in claim 35 wherein said switchable beamsplitter additionally comprises internal reflecting means which cause light beams entering said beamsplitter to be reflected by 180 degrees so that light beams exiting said beamsplitter are substantially parallel with light beams entering said beamsplitter.

37. An apparatus as claimed in claim 36 wherein the said components of said switchable beamsplitter has a first reflecting face orientated such that light beams entering said beamsplitter will be reflected to be incident upon said interface at an angle slightly greater than the criti-cal angle of said interface in said unswitched state; and a second reflecting face orientated to said first reflecting face at substantially 90 degrees.

38. An apparatus as claimed in claim 35, 36 or 37 wherein one or both of said parallel faces of said beam-splitter are coated with a thin dichroic film so that in said unswitched state, light beams reflected at said inter-face will form substantially natural colored images and in said switched state, one polarization component will be divided into two different color groups, one of said color groups being transmitted across said interface, and the other of said color groups being reflected at said inter-face.

39. An apparatus as claimed in claim 1, 3, 4-23, 26, 35-38 wherein one or more photosensitive components or photodetectors are placed in the image plane of the paths of said light beams, to aid in achieving greater resolution of the images defined by said light beams.